A routine examination on a muscular injury Rossi, 27, picked up recently revealed that the knee which was operated on last January was showing signs of having been overburdened. He was told to rest for a week before further tests would be carried out to see whether the knee had improved after a rest.

Those tests took place on Monday, and they showed a "clinical improvement" in his knee, albeit "confirming the overburdening" first seen on Aug. 18, according to a club statement.

The Italy international has therefore been ruled out of Saturday's Serie A opener at Roma, but he could well be sidelined for longer.

"Next week, after further physiotherapy, a specialist will evaluate the injury," the club statement continued.

Those tests will determine whether the conservative treatment Rossi is currently receiving is sufficient to restore the knee to full strength or whether he may need to be operated on again.

It would be the fourth time Rossi has required surgery and the recovery time could see him miss several months of action.

Almost certainly, he will not figure among the names new Italy coach Antonio Conte calls up on Saturday for his first two games in charge of the national team.